Abstract
Anabolism and catabolism are tightly regulated according to the cellular energy supply. Upon energy stress, ribosomal RNA (rRNA) biogenesis is inhibited, and autophagy is induced. However, the mechanism linking rRNA biogenesis and autophagy is unclear. Here, we demonstrate that the nucleolar protein NAT10 plays a role in the transition between rRNA biogenesis and autophagy. Under normal conditions, NAT10 is acetylated to activate rRNA biogenesis and inhibit autophagy induction. Mechanistic studies demonstrate that NAT10 binds to and acetylates the autophagy regulator Che-1 at K228 to suppress the Che-1-mediated transcriptional activation of downstream genes Redd1 and Deptor under adequate energy supply conditions. Upon energy stress, NAT10 is deacetylated by Sirt1, leading to suppression of NAT10-activated rRNA biogenesis. In addition, deacetylation of NAT10 abolishes the NAT10-mediated transcriptional repression of Che-1, leading to the release of autophagy inhibition. Collectively, we demonstrate that the acetylation status of NAT10 is important for the anabolism-catabolism transition in response to energy stress, providing a novel mechanism by which nucleolar proteins control rRNA synthesis and autophagy in response to the cellular energy supply.